I started noticing hair loss around the age of 25 especially in the crown area. I have been on finasteride on and off for the last 5 years.
I use that coupled with Nixoral shampoo and topical rogaine and have regained pretty much all of what I lost before. I just finished a 10 week cycle (my first) and gained a solid 15+ pounds, so I don't think it inhibited the test I was taking.
At any rate, I have not noticed any deleterious effects and am a fan of the substance, although I have heard it only works for around 80 percent of men.
As a final note, I would try and get a script for proscar vs. propecia, it's the same drug (finasteride) only in 5 mg tabs instead of 1 mg. The thing is, insurance will cover proscar, and you can divide the pills so you basically get a 4 month supply for whatever your co-pay is. Hope that helps!